American private equity group JC Flowers is lining up bids for at least four UK building societies as part of an audacious plan to create a "supermutual" that could be partially floated on the London stock market in five years.

West Bromwich, Skipton, Norwich & Peterborough and Principality are in his sights; together, they have more than 1.7 million members.

Former Goldman Sachs banker Christopher Flowers, who founded the US private equity firm, is already acquiring a 40% stake in Kent Reliant, which has a membership of 180,000. Kent would be a platform for further UK expansion, with Flowers aiming to create a business unique to the UK but which mirrors the structure of Crédit Agricole. The French institution is 60% owned by 39 retail co-operative banks, with the remaining shares traded on the Paris exchange.

Flowers wants to build up a minority holding in a newly created British super-mutual that could be sold via a partial flotation. Conversion could involve a "sweetener" to members in the form of free shares, as well as a promise that members would keep overall control.

Harvard-educated Flowers, 52, describes his model as a hybrid mutual with publicly quoted stock. The idea is create an organisation embracing mutuality as well as free market capitalism.

Analysts say many UK societies are struggling as regulators force them to hold extra capital in the wake of the financial crisis, but, unlike banks, they cannot tap shareholders for funds. Neither can they turn to the debt markets, which remain largely shut. "That means a capital infusion from a private equity group could be a perfect solution," says an observer.

David Morgan, head of JC Flowers in Europe, says his priority is to complete the deal with Kent that will see the firm inject £50m, as he looks at other societies: "This is a very fragmented industry, ripe for consolidation." Kent's members vote on the deal in November.

Asked if he thought private equity involvement with building societies was a weird notion, Morgan said: "Societies and private equity make good bedfellows as our project will demonstrate."

Flowers, who made a fortune turning around a failing bank in Japan, could make another pile from his experiment. The private equity firm owns preferential shares in Kent that convert to common equity in the event of a flotation. Flowers will acquire preferential stock when it acquires other societies to maximise returns.

But Flowers – who once described himself as a "lowlife grave dancer" – has other options. The main one is to use his ownership of Kent Reliant to launch a bid for Northern Rock, the mortgage lender rescued by the taxpayer in 2008 which is likely to be sold by the government next year. Flowers bid for the Rock two years ago, prior to its privatisation by former chancellor Alistair Darling. He tried unsuccessfully to take over Friends Provident in 2009.

Insiders say creating a supermutual holds great personal appeal for Flowers. He is attempting something similar in Spain where he has bought one of the country's mutually-owned regional savings banks, Banca Civica.

West Bromwich building society, which hit financial difficulties last year, could find an injection of capital from Flowers attractive, as could the Skipton, whose former boss, John Goodfellow, has joined JC Flowers as an adviser.

Adrian Coles, of the Building Societies Association, described the Flowers/Kent deal as "intelligent and innovative".